I try to maintain my balance from time to time when I ride the subway here in the DC area. I really have to shift my hips in the opposite direction of the subway in an attempt to not to move my feet. I first saw this being done when I was visiting Tokyo. I was amazed on how many riders didn't have to hold on to anything, read a newspaper or magazine, and still stay perfectly still. They don't shift their hips or anything. I'm trying to emulate them as best I can.